Clamp for pattern recognition

ABSTRACT

A lead frame such as a normal or inverted lead frame includes an unsymmetrical part such as a gate. A clamp, for clamping the lead frame during wire bonding, includes an observation hole. The unsymmetrical part of the lead frame is visible through the observation hole. A lead eye box and a lead eye point are set on the unsymmetrical part through the observation hole. The picture inside the lead eye box is captured and compared to a control picture. Setting the lead eye box and the lead eye point on the unsymmetrical part through the observation hole allows detection of when the lead frame is inadvertently rotated at prescribed angles or when a normal lead frame and an inverted lead frame are inadvertently mixed.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a clamp for pattern recognition.More particularly, the present invention relates to a clamp used forclamping and detecting the orientation of a normal lead frame or aninverted lead frame during a wire bonding process and also to detectingthe orientation of symmetrical dies (semiconductor chips).

[0003] 2. Description of the Related Art

[0004] In general, wire bonding is a process that connects leads to eachother. For example, in die wire bonding, bond pads formed on the surfaceof the die are electrically connected to leads of a substrate such as aprinted circuit board, a circuit tape, a circuit film, a lead frame, orthe like. For simplicity, the substrate shall hereinafter be referred toas a lead frame although it is understood that other substrates can beused.

[0005] A wire bonding device 900 for wire bonding is shown in FIG. 9.Wire bonding device 900 includes a camera 902 for capturing a picture, amonitor 904 for displaying the picture captured by the camera 902, amemory 906 for storing the positions of a lead frame 908 and a die (notshown), e.g., the positions are input by an initial operator, a centralprocessing unit 910 for performing a general control such as dataprocessing and input/output, a transfer unit 912 for transferring thelead frame 908, and a wire bond control unit 914 for moving andcontrolling a bond head 916, on which a capillary (not shown) and thecamera 902 are mounted, in the axis of X, Y and Z. The aboveconstruction is well known.

[0006] A conventional method, which recognizes a pattern of the leadframe 908 and of the die using the wire bonding device 900 will bedescribed as follows. First, the construction of a lead frame and aclamp used during the bonding of the lead frame will be describedhereinafter.

[0007] Referring to FIG. 10A, a typical normal lead frame NLF includes aspace 3 of a prescribed size formed at the center and a frame body 2 ofa board type formed at both sides of the space 3 for maintaining andsupporting the whole structure. A die pad 4 of a rectangular board typeto mount a die 30 during the manufacturing process is disposed at thecenter of the space 3. The die pad 4 has four edges, to which ends offour tie bars 5 are connected respectively. Three of the tie bars 5 areconnected to buffing connection boards 18 at the other endsrespectively. The buffing connection boards 18 are connected to theframe body 2. The other of the tie bars 5 is connected to a gate 16(shown at the upper and left edge of FIG. 10A) serving to make resineasily flow toward the die pad 4 during the manufacturing process(molding step). The gate 16 is connected to the frame body 2.

[0008] Here, the gate 16 has a dent part 16A formed at one side thereofto indicate the position of the gate 16 and to allow the normal leadframe NLF to be easily discriminated from an inverted lead frame (ILF),which will be described hereinafter. Moreover, each of the tie bars 5 isbent downwardly with a prescribed slant in a specific area in such amanner that the die pad 4, which is connected and supported by the tiebars 5 is located at a lower area than the frame body 2, i.e., isdownset.

[0009] Meanwhile, a plurality of inner leads 6 are arranged around thedie pad 4 radially in prescribed intervals from the die pad 4.Furthermore, the inner leads 6 are connected to a plurality of outerleads 10, respectively. Ends of the outer leads 10 are integrallyconnected to straight support bars 12. Additionally, the straightsupport bars 12 are connected to a plurality of bent support bars 14.The bent support bars 14 are connected to the frame body 2.

[0010] Between the inner leads 6 and the outer leads 10, a dambar 8 isprovided at right angles to the longitudinal direction of the innerleads 6 or the outer leads 10. The dambar 8 serves to prevent resin fromoverflowing to the outer leads 10 during molding.

[0011]FIG. 10B is a plan view showing an example of a conventionalinverted lead frame ILF. Note that the gate 16 for injecting resin(shown at the upper and right edge of FIG. 10B) is at a differentlocation compared to the gate 16 of the normal lead frame NLF.

[0012] Illustrated in FIGS. 10A and 10B are an adhesive tape 22 forpreventing the short or bending of the inner leads 6, an index hole 1for detecting or fixing the orientation of the lead frame NLF or ILF,and a passivation layer 33, sometimes called a glass or glassificationlayer, coated on the surface of the die 30.

[0013]FIG. 11 is a perspective view of a conventional clamp 1100. Use ofclamp 1100 with regards to normal lead frame NLF (FIG. 10A) ishereinafter described although it is understood that clamp 1100 is usedwith inverted lead frame ILF (FIG. 10B) in a similar manner. Referringnow to FIGS. 10A and 11 together, the clamp 1100 serves to fix thenormal lead frame NLF not to move during the wire bonding process in thestate that the normal lead frame NLF on which the die 30 is mounted, isseated on a heater block (not shown) of the wire bonding device 900(FIG. 9) by the transfer unit 912. The clamp 1100 has a window 1140being in the form of a quadrangle in such a manner that a prescribedarea of the die pad 4, the inner leads 6 and the tie bars 5 of thenormal lead frame NLF is opened outward.

[0014] Continuously, referring now to FIGS. 12, 13A, 13B, 13C, 13D, 13Eand 14, the conventional method for recognizing a pattern for wirebonding will be described.

[0015] Referring now to FIGS. 12 and 13A together, in a lead frameorientation detecting step 1202, a sensor senses index holes 1 of thenormal lead frame NLF, which is loaded on the heater block (not shown)by the transfer unit 912 (FIG. 9), and it is determined whether or notthe normal lead frame NLF is loaded in an exact direction. Here, if thenormal lead frame NLF is loaded in the contrary direction, the positionand the number of the index holes 1 are changed, and thereby the badloaded state of the normal lead frame NLF can be sensed. Furthermore, atthis time, the normal lead frame NLF is not completely clamped by theclamp 1100.

[0016] Referring now to FIGS. 12, 13A and 13B together, in a first leadframe indexing step 1204, a camera, e.g., camera 902 of FIG. 9, and apattern recognition system (PRS), which converts a picture captured bythe camera into an electric signal, set a lead eye box LEB1 and a leadeye point LEP1 on one tie bar 5, for example, on the tie bar 5 locatedat the upper and left end inside the window 1140 of the clamp 1100 ofthe normal lead frame NLF as best shown in FIG. 13B. Generally, a lead(die) eye box is an image of an area and a lead (die) eye point is aspecific location, i.e., point, within the lead (die) eye box.

[0017] The camera and PRS capture the picture, and it is determinedwhether or not the captured picture is identical with a first controlpicture previously stored in the memory, e.g., in memory 906 of FIG. 9,within the permitted range. If the captured picture is identical withthe first control picture stored in the memory, the next step isprogressed. If the captured picture is identical with the first controlpicture within the permitted range, the normal lead frame NLF is movedin the axes of X and Y, e.g., horizontally and vertically in the view ofFIG. 13A, to make the captured picture be identical with the firstcontrol picture. Moreover, if the captured picture is different from thefirst control picture beyond the permitted range, further steps arestopped and an operator's input is waited for.

[0018] Here, the PRS is the most advanced technique of pictureinformation processing systems. The PRS is widely used forsemiconductors, measuring instruments, material analysis, medicalscience fields and military affairs. Such PRS is applied to thesemiconductor field, especially, the wire bonding device 900 (FIG. 9).The general principle of the PRS is that the control picture stored inthe memory and the picture captured by the camera are compared and adetermination is made whether or not the captured picture is identicalwith the control picture. If the captured picture is identical with thecontrol picture to within the permitted range, the normal lead frame NLFor the camera is moved in the axes of X and Y to make the capturedpicture of the lead frame be identical with the control picture storedin the memory.

[0019] Referring now to FIGS. 12, 13A, 13B and 13C together, after thenormal lead frame NLF is clamped with the clamp 1100, in a second leadframe indexing step 1206, the camera and the PRS set the first lead eyebox LEB1 and the first lead eye point LEP1 on one tie bar 5 of thenormal lead frame NLF as best shown in FIG. 13B. A determination is madeas to whether or not the captured picture is identical with the firstcontrol picture stored in the memory within the permitted range. If thecaptured picture is identical with the first control picture stored inthe memory, the next step is progressed. If the captured picture isidentical with the first control picture to within the permitted range,the camera is moved in the axes of X and Y to make the captured picturebe completely identical with the first control picture.

[0020] Continuously, a second lead eye box LEB2 and a second lead eyepoint LEP are set on another tie bar 5, for example, on the tie bar 5located at the lower and right end inside the window 1140 of the clamp1100, of the normal lead frame NLF as best shown in FIG. 13C. Thepicture is captured and a determination is made as to whether or not thecaptured picture is identical with a second control picture stored inthe memory within a permitted range. If the captured picture isidentical with the second control picture, the next step is progressed.If the captured picture is identical with the second control picture towithin the permitted range, the camera is moved in the axes of X and Yto make the captured picture be completely identical with the secondcontrol picture.

[0021] Here, when the first and second lead eye boxes LEB1, LEB2 areset, if either of the captured pictures are different from therespective control pictures beyond the permitted range, further stepsare stopped and the operator's input is waited for. That is, theoperator sets the lead eye boxes LEB1, LEB2 and the lead eye pointsLEP1, LEP2 manually to set the normal lead frame NLF in an exactposition.

[0022] In a Video Lead Locator (VLL) step 1208, the camera reads theposition of each inner lead 6 of the normal lead frame NLF and storesthe position in the memory.

[0023] Referring now to FIGS. 12, 13A, 13D and 13E together, in a dieorientation detecting step 1210, the edge of the die 30 and two or morebond pads P formed in the vicinity of the edge of the die 30 are set asa first die eye box DEB1 and a first die eye point DEP1 as best shown inFIG. 13D. The picture is captured, and the captured picture is comparedwith a third control picture stored in the memory. If the capturedpicture is identical with the third control picture stored in thememory, the next step is progressed. If the captured picture isidentical with the third control picture within the permitted range, thecamera is moved in the axes of X and Y to make the captured picture becompletely identical with the third control picture, and then, the nextstep is progressed. If the captured picture is different from the thirdcontrol picture beyond the permitted range, further steps are stoppedand the operator's input is waited for (the operator then finds andinputs the first die eye box DEB1 and the first die eye point DEP1manually).

[0024] Continuously, in the same way, a second die eye box DEB2 and asecond die eye point DEP2 are set in the vicinity of another edge of thedie 30 as best shown in FIG. 13E. After the same steps are performed, ifthe captured picture is completely identical with a fourth controlpicture stored in the memory, the next step is progressed. If thecaptured picture is identical with the fourth control picture within thepermitted range, the camera is moved in the axes of X and Y to make thecaptured picture be completely identical with the fourth controlpicture, and the next step is progressed. If the captured picture isdifferent from the fourth control picture beyond the permitted range,further steps are stopped and the operator's input is waited for.

[0025] Continuously, referring now to FIG. 14, a virtual straight line35 is drawn between die eye points DEP1, DEP2 and a central point CP ofthe virtual straight line 35 is compared with a control central pointstored in the memory (e.g., stored in the memory by the operator whenthe die is loaded initially). If the central point CP is identical withthe control central point within the permitted range, the next step isprogressed, but if they are not identical, further steps are stopped andthe operator's input is waited for.

[0026] Continuously, based on the central point CP, the positions andthe coordinates of all bond pads P (i.e., bond pads P1, . . . , Pn) ofthe die 30 are calculated.

[0027] For example, if the position and the coordinate of a first bondpad P1 from the central point CP is calculated, the positions of theremaining bond pads P2, P3, . . . , Pn can be all calculated. In moredetail, since the relative or absolute positions of all bond pads P areinitially stored in the memory, if only the position of the first bondpad Pi is found, coordinates of the remaining bond pads P2, P3, . . . ,Pn can be automatically found.

[0028] In FIGS. 13D, 13E and 14, probe marks 31 are formed by contactingbond pads P with a probe when the die 30 is tested in the electricalefficiency and a passivation layer 33, which protects the upper surfaceof the die 30 from the outside is illustrated.

[0029] Referring now to FIGS. 12, 13A, 13B, 13C, 13D and 13E, in a wirebonding step 1212, the bond pads P of the die 30 and the inner leads 6of the normal lead frame NLF are bonded with a conductive wire using thepositions and the coordinates of the die 30 and the normal lead frameNLF and the capillary of the bond head. The bonding is started from thefirst bond pad P1 of the die 30 and a first inner lead 6 of the normallead frame NLF.

[0030] Even though the normal lead frame NLF or the die 30 are tilted orhave error in the position, if they are within the permitted range, thebond pads P of the die 30 and the inner leads 6 of the normal lead frameNLF can be all wire-bonded.

[0031] However, the conventional pattern recognition method and clamphave the following problems.

[0032] First, the lead eye boxes LEB1, LEB2 and the lead eye pointsLEP1, LEP2 for the first and second lead frame indexing steps 1204, 1206are set on the tie bars 5 located inside the window 1140 of the clamp1100. Since the normal lead frame NLF is symmetric, if the normal leadframe NLF is inadvertently rotated at an angle of 180 degrees when itenters the wire bonding, this inadvertent rotation, sometimes calledmisalignment, cannot be detected. The structure of the die pad 4 and ofthe tie bars 5 connected to the die pad 4 shown through the window 1140of the clamp 1100 are in a complete symmetrical form, and thereby, ifthe normal lead frame NLF is rotated at an angle of 180 degrees, thewire bonding device cannot detect it. Such problem occurs morefrequently when the normal lead frame NLF and the inverted lead frameILF are used together.

[0033] Even though, in the lead frame orientation detecting step 1202,the index holes 1 are counted and the direction is detected, thedetection is performed inaccurately due to pollution of the normal leadframe NLF or the sensor. Therefore, there is much possibility that themisaligned normal lead frame NLF will pass the lead frame orientationdetecting step 1202.

[0034] Second, since the lead eye boxes LEB1, LEB2 and the lead eyepoints LEP1, LEP2 are located at the center of the heater block on whichheat is concentrated, the normal lead frame NLF is rapidly oxidized andthe color of the normal lead frame NLF becomes similar with that of theheat block, and thereby the pictures cannot be exactly captured. Thatis, the picture recognition is lowered.

[0035] Third, if the die 30 is inadvertently bonded in rotation atangles of 90 degrees, 180 degrees or 270 degrees, this misalignment ofthe die 30 cannot be detected and the wire bonding is performed on themisaligned die 30.

[0036] That is, recently, the die 30, which has bond pads P ofsymmetrical type in all directions, is widely used, and sometimes, thedie 30 is misaligned and bonded in rotation at prescribed angles, forexample, 90 degrees, 180 degrees or 270 degrees, in a die bonding step.In that case, the position of the first bond pad Pi is changed, however,it cannot be detected through the above pattern recognition method.Therefore, the central processing unit incorrectly determines that thedie 30 is bonded in the correct position and performs the wire bonding.However, actually, as the first bond pad P1 is located in a differentarea, the wire bonding of all bond pads P and the inner leads G goeswrong. Therefore, only during the electrical test performed after thewire bonding is finished is the defect detected thereby sharply loweringthe production efficiency.

[0037] Fourth, as the bond pads P are finely pitched, the picturerecognition rate by the PRS is lowered when the die eye boxes DEB1, DEB2and the die eye points DEP1, DEP2 are set. That is, the closer thedistance between the bond pads P is, the smaller the area of the bondpads P is, but the size of the probe mark 31 formed during theelectrical test of the die 30 is not reduced. Therefore, if the pictureinside the die eye boxes DEB1, DEB2 is converted into an electricsignal, as the color of the probe mark 31 (for example, black color)takes the larger area than the color of the bond pad P (for example,white color), in the probability, all the bond pads P may be convertedinto electric signal of black color, and thereby the picture recognitionrate is lowered. Therefore, there occurs trouble that the operator mustdetect orientation of the die 30 manually. Here, the probe mark 31 is ablack mark formed by the contact of the probe when the efficiency andthe validity of the die 30 are tested.

[0038] Fifth, the passivation layer 33 is covered on the surface of thedie 30 to protect various circuits to the inside of rows in which thebond pads P are formed, and thereby the color of the surface is shown invarious colors or rainbow colors. The phenomenon is more deepened byheat provided during a sawing step of a wafer or various manufacturingsteps. By the change of color, the camera cannot exactly recognize thepicture inside the die eye boxes DEB1, DEB2, and thereby the picturerecognition rate is lowered.

SUMMARY OF THE INVENTION

[0039] In accordance with the present invention, a method of patternrecognition, which can detect a state that a lead frame is rotated atprescribed angles or the orientation of a normal lead frame and aninverted lead frame is presented.

[0040] The method improves a picture recognition rate by setting a leadeye box and a lead eye point in an area other than the central portionof a lead frame on which heat is concentrated.

[0041] Further, the method detects if the die is misaligned on a diepad, i.e., when the die is inadvertently rotated at prescribed angles(90 degrees, 180 degrees or 270 degrees). The orientation of the die isdetected even though the area of the bond pads is reduced as the bondpads are pitched finely.

[0042] Further, the orientation of the die is detected even though thecolor of the die is changed by a passivation layer formed inside rows ofbond pads of the die.

[0043] Also, in accordance with the present invention, a clamp, whichclamps a lead frame, is presented.

[0044] In one embodiment, a method for recognizing a pattern comprises:a lead frame orientation detecting step of setting a first lead eye boxand a first lead eye point on a gate of a lead frame through anobservation hole of a clamp and setting a second lead eye box and asecond lead eye point on a support bar of the lead frame located on theouter circumference of the clamp with a camera, before clamping the leadframe seated on a heater block with the clamp, and determining whetheror not the lead frame is seated in an exact position; a lead frameindexing step of setting the first lead eye box and the first lead eyepoint on the gate and the second lead eye box and a second lead eyepoint on the support bar with the camera, after clamping the lead frame,and determining whether or not the lead frame is seated in the exactposition; a VLL (Video Lead Locate) step of capturing the positions ofleads of the lead frame newly and memorizing the positions; and a dieorientation detecting step of setting die eye boxes and die eye pointson two specific areas of bond pads of edges of a die and determiningwhether or not the die is mounted in an exact position.

[0045] In the lead frame orientation detecting step and the lead frameindexing step, the first lead eye box and the first lead eye point seton the gate are set on one of a plated layer or a dent part formed onthe gate.

[0046] Moreover, the lead frame orientation detecting step furtherincludes a step of moving the lead frame in the axes of X and Y in aprescribed distance and making the captured picture be identical with amemorized control picture completely if the captured picture inside thefirst lead eye box is identical with the memorized control picturewithin a permitted range.

[0047] Furthermore, the lead frame indexing step further includes a stepof moving the camera in the axes of X and Y in a prescribed distance andmaking the captured picture be identical with the memorized controlpicture completely if the captured picture inside the first lead eye boxis identical with the memorized control picture within a permittedrange.

[0048] Additionally, the lead frame orientation detecting step and thelead frame indexing step, respectively, further include a step ofstopping the operation and waiting for an operator's input if there isdifference between the picture captured by the camera and the memorizedcontrol picture beyond the permitted range.

[0049] In another embodiment, the present invention provide a method forrecognizing patterns comprises: a lead frame orientation detecting stepof sensing the hole number of a lead frame seated on a heater block anddetermining whether or not the lead frame is seated in an exact firstposition; a first lead frame indexing step of setting a first lead eyebox and a first lead eye point on a tiebar of the lead frame with acamera before clamping the lead frame with a clamp, and determiningwhether or not the lead frame is seated in the exact first position; asecond lead frame indexing step of setting lead eye boxes and lead eyepoints on two tie bars of the lead frame with the camera after clampingthe lead frame with the clamp, and redetermining whether or not the leadframe is seated in the exact first position; a VLL (Video Lead Locate)step of newly capturing the positions of leads of the lead frame withthe camera and memorizing the positions; and a die orientation detectingstep of setting die eye boxes and die eye points on two specificpatterns of edges of a die with the camera and determining whether ornot the die is mounted in an exact second position.

[0050] In yet another embodiment, a method for recognizing patternscomprises: a lead frame orientation detecting step of setting a firstlead eye box and a first lead eye point on a gate of a lead framethrough an observation hole of a clamp and setting a second lead eye boxand a second lead eye point on a support bar of the lead frame locatedon the outer circumference of the clamp with a camera, before clampingthe lead frame seated on a heater block with the clamp, and determiningwhether or not the lead frame is seated in an exact first position; alead frame indexing step of setting the first lead eye box and the firstlead eye point on the gate and setting the second lead eye box and thesecond lead eye point on the support bar with the camera, after clampingthe lead frame, and determining whether or not the lead frame is seatedin the exact first position; a VLL (Video Lead Locate) step of capturingthe positions of leads of the lead frame newly and memorizing thepositions; and a die orientation detecting step of setting die eye boxesand die eye points on specific patterns of edges of a die anddetermining whether or not the die is mounted in an exact secondposition.

[0051] The die orientation detecting step sets the die eye boxes and thedie eye points on the specific patterns formed in the vicinity of theedges located outside the bond pads of the die. The specific patternsare pictures, figures, characters or numbers. The die orientationdetecting step stops the operation and waits for an operator's input ifthe specific patterns are not located inside the die eye boxes.

[0052] The clamp includes a window formed to expose upward the diemounted on a die pad of the lead frame and leads on the outercircumference of the die during a wire bonding process and at least oneor more observation holes formed in the outer circumference of thewindow to set a gate of the lead frame as a lead eye box and a lead eyepoint.

[0053] The clamp has observation holes located in opposite positions ofthe outer circumference of the window to detect the orientation not onlyof a normal lead frame but also of an inverted lead frame.

[0054] Advantageously, the orientation of the lead frame is exactlydetected by setting the first lead eye box and the first lead eye pointon specific shape parts, which are not symmetrical parts, i.e., on aplated layer or the dent part formed on the gate and the support bar ofthe lead frame. This allows detection of when the lead frame isinadvertently rotated at prescribed angles, for example, 180 degrees, orthe normal lead frame and the inverted lead frame are inadvertentlymixed.

[0055] Further, by setting the first lead eye box and the first lead eyepoint in an area other than the central portion of the lead frame onwhich heat is concentrated, the picture recognition rate of the PRS isimproved.

[0056] Further, by adopting not the bond pads but the specific patternsformed at the edge of the die as a basic picture, when the symmetricaldie is misalign and bonded in rotation at prescribed angles, forexample, 90 degrees, 180 degrees or 270 degrees, this misalignment isdetected promptly.

[0057] Also, even though the bond pads are pitched finely, since the dieeye boxes and the die eye points adopt not the bond pads but thespecific patterns formed at the outside of the bond pads as the basicpicture, the picture recognition rate is improved.

[0058] In addition, since the die eye boxes and the die eye points areset at the outer circumference of the bond pads where the passivationlayer is not formed, inaccurate picture information due to the change ofthe color of the passivation layer is not provided, thereby improvingthe picture recognition rate by the PRS.

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Further advantages of the invention can be more fully understoodfrom the following detailed description taken in conjunction with theaccompanying drawings in which:

[0060]FIG. 1 is a flow chart of an embodiment of a pattern recognitionmethod according to the present invention;

[0061]FIG. 2 is a flow chart of another embodiment of the patternrecognition method according to the present invention;

[0062]FIG. 3 is a flow chart of yet another embodiment of the patternrecognition method according to the present invention;

[0063]FIG. 4A is a view illustrating a method of orientation andindexing a lead frame according to the present invention;

[0064]FIGS. 4B and 4D are enlarged plan views of the region IVB of FIG.4A in accordance with alternative embodiments of the present invention;

[0065]FIG. 4C is an enlarged plan view of the region IVC of FIG. 4A inaccordance with one embodiment of the present invention;

[0066]FIG. 5A is a view illustrating a method of die orientationaccording to the present invention;

[0067]FIGS. 5B and 5C are enlarged plan views of the regions VB, VC,respectively, of FIG. 5A in accordance with one embodiment of thepresent invention;

[0068]FIG. 6 is a view showing an example for calculating the positionof bond pads formed on a die;

[0069]FIG. 7A is a view illustrating a method of detecting that a diehas been inadvertently rotated and bonded to a normal lead frame inaccordance with the present invention;

[0070]FIGS. 7B and 7C are enlarged plan views of the regions VIIB, VIIC,respectively, of FIG. 7A in accordance with one embodiment of thepresent invention;

[0071]FIGS. 8A to 8C are perspective views of a clamp according tovarious embodiments of the present invention;

[0072]FIG. 9 is a block diagram of a construction of a wire bondingdevice in accordance with the prior art;

[0073]FIGS. 10A and 10B are plan views showing a die mounted to a normallead frame and inverted lead frame, respectively, in accordance with theprior art;

[0074]FIG. 11 is a perspective view of a clamp in accordance with theprior art;

[0075]FIG. 12 is a flow chart showing a pattern recognition method inaccordance with the prior art;

[0076]FIG. 13A is a view of a lead frame and die during orientation andindexing in accordance with the prior art;

[0077]FIGS. 13B, 13C, 13D and 13E are enlarged plan views of the regionsXIIIB, XIIIC, XIIID, XIIIE, respectively, of FIG. 13A in accordance withthe prior art; and

[0078]FIG. 14 is a view showing an example for calculating the positionof bond pads formed on a die using a conventional pattern recognitionmethod.

DETAILED DESCRIPTION

[0079] The present invention will now be described in detail inconnection with various embodiments with reference to the accompanyingdrawings. For reference, like reference characters designatecorresponding parts throughout several views.

[0080]FIG. 1 is a flow chart of a pattern recognition method accordingto one embodiment of the present invention.

[0081] 1. Referring now to FIGS. 1, 4A, 4B and 4D together, in a leadframe orientation detecting step 100, a lead eye box LEBA, e.g., a firstlead eye box, and a lead eye point LEPA, e.g., a first lead eye point,are set on a gate 16 of a normal lead frame NLF, e.g., such as thatshown in FIG. 10A, as best shown in FIG. 4B or 4D. Further, a lead eyebox LEBB, e.g., a second lead eye box, and a lead eye point LEPB, e.g.,a second lead eye point, are set on a support bar 14 of the normal leadframe NLF located on the outer circumference of a clamp 400 as bestshown in FIG. 4C. Specifically, gate 16 (FIG. 4B) is shown through anobservation hole 41A of a clamp 400. The lead eye boxes LEBA, LEBB andthe lead eye points LEPA, LEPB are set before the normal lead frame NLF,which is seated on a heater block, is clamped completely by the clamp400. As set forth below, it is determined whether or not the normal leadframe NLF is seated in an exact direction and position, sometimes calledan exact first direction and first position.

[0082] That is, first, the lead eye box LEBA and the lead eye point LEPAare set on a dent part 16A or on a plated layer 16B formed on the gate16 of the normal lead frame NLF and the picture inside the lead eye boxLEBA is captured as best shown in FIGS. 4B, 4D, respectively. Adetermination is made as to whether or not the captured picture isidentical with a first control picture stored in a memory within apermitted range. For example, the captured picture is compared to thefirst control picture and the difference, if any, between the capturedand first control picture is analyzed to determine if the difference iswithin an acceptable, sometimes called permitted, range of differences.Control pictures including the first control picture are loaded into thememory of the wire bonding device by the initial operator in aconventional manner. Further, those of skill in the art will understandthat the permitted range as used herein depends on the particular leadframe, die and wire bonding device used.

[0083] If the captured and first control pictures are completelyidentical with each other, the next step is progressed. If the capturedand first control pictures are identical with each other within thepermitted range, the normal lead frame NLF is moved in the axes of X andY to make the captured picture and the first control picture becompletely identical with each other. Meanwhile, if there is differencebetween the captured picture and the first control picture beyond thepermitted range, the operation is stopped and an operator's input iswaited for. In the above case, the operator finds the gate 16 of thenormal lead frame NLF and sets the lead eye box LEBA and the lead eyepoint LEPA manually.

[0084] Here, the plated layer 16B (FIG. 4B) is made of at least one ofaluminum (Al), silver (Au), gold (Ag), palladium (Pd), nickel (Ni), lead(Pb) and tin (Sn) alloys although other materials are used in otherembodiments.

[0085] Continuously, second, the lead eye box LEBB and the lead eyepoint LEPB (FIG. 4C) are set on the support bar 14 of the normal leadframe NLF and the picture is captured, i.e., the picture inside of thelead eye box LEBB is captured. A determination is made as to whether ornot the captured picture is identical with a second control picturestored in the memory within a permitted range. If the captured andsecond control pictures are completely identical with each other, thenext step is progressed. If the captured and second control pictures areidentical with each other within the permitted range, the normal leadframe NLF is moved in the axes of X and Y to make the captured pictureand the second control picture be completely identical with each other.If there is difference between the captured picture and the secondcontrol picture beyond the permitted range, the operation is stopped andthe operator's input is waited for. In the above case, the operatorfinds the support bar 14 of the normal lead frame NLF and sets the leadeye box LEBB and the lead eye point LEPB manually.

[0086] 2. In a lead frame indexing step 120, the lead eye boxes LEBA,LEBB and the lead eye points LEPA, LEPB are set again on the gate 16 andon the support bar 14, respectively, of the normal lead frame NLF by thecamera after the normal lead frame NLF is completely clamped on theheater block with the clamp 400. A determination is made again as towhether or not the normal lead frame NLF is seated in the exact positionto detect whether or not the position of the normal lead frame NLFchanged during the clamping of the normal lead frame NLF with the clamp400.

[0087] That is, first, the lead eye box LEBA and the lead eye point LEPAare set on the dent part 16A or the plated layer 16B formed on the gate16 of the normal lead frame NLF as best shown in FIGS. 4D, 4B,respectively, and the picture inside of the lead eye box LEBA iscaptured. A determination is made as to whether or not the capturedpicture is identical with the first control picture stored in the memorywithin the permitted range. If the captured and first control picturesare completely identical with each other, the next step is progressed.If the captured and first control pictures are identical with each otherwithin the permitted range, the camera is moved in the axes of X and Yto make the captured picture and the first control picture be completelyidentical with each other. Meanwhile, if there is difference between thecaptured picture and the first control picture beyond the permittedrange, the operation is stopped and the operator's input is waited for.In the above case, the operator finds the gate 16 of the normal leadframe NLF and sets the lead eye box LEBA and the lead eye point LEPAmanually.

[0088] Continuously, second, the lead eye box LEBB and the lead eyepoint LEPB (FIG. 4C) are set on the support bar 14 of the normal leadframe NLF and the picture inside of the lead eye box LEBB is captured. Adetermination is made as to whether or not the captured picture isidentical with the second control picture stored in the memory withinthe permitted range. If the captured and second control pictures arecompletely identical with each other, the next step is progressed. Ifthe captured and second control pictures are identical with each otherwithin the permitted range, the camera is moved in the axes of X and Yto make the captured picture and the second control picture becompletely identical with each other. If there is difference between thecaptured picture and the second control picture beyond the permittedrange, the operation is stopped and the operator's input is waited for.In the above case, the operator finds the support bar 14 of the normallead frame NLF and sets the lead eye box LEBB and the lead eye pointLEPB manually.

[0089] 3. In a VLL (Video Lead Locator) step 140, the positions of innerleads 6 of the normal lead frame NLF are captured by the camera newlyand stored in the memory.

[0090] 4. In a die orientation detecting step 160, die eye boxes and thedie eye points are set on two specific areas of bond pads P of the edgesof the die 30 mounted on the die pad 4 of the normal lead frame NLF bythe camera, and it is determined whether or not the die 30 is mounted inan exact direction. Since the die orientation detecting step 160 isidentical with the die orientation detecting step 1210 (FIG. 12) of theconventional method, its description will be omitted.

[0091] 5. In a wire bonding step 180, the general wire bonding isperformed in the state that the position and direction of the normallead frame NLF and the position and direction of the die 30 are set inprescribed places.

[0092] Advantageously, the orientation of the normal lead frame NLF isexactly detected by setting the lead eye boxes LEBA, LEBB and the leadeye points LEPA, LEPB on specific shaped parts, which are notsymmetrical parts, sometimes called unsymmetrical parts, i.e., on thedent part 16A (FIG. 4D) or the plated layer 16B (FIG. 4B) and thesupport bar 14 (FIG. 4C), respectively. This allows detection of whenthe normal lead frame NLF is inadvertently rotated at prescribed angles,for example, 180 degrees, or the normal lead frame NLF and an invertedlead frame ILF such as that illustrated in FIG. 10B are inadvertentlymixed.

[0093] Moreover, by setting the lead eye boxes LEBA, LEBB and the leadeye points LEPA, LEPB in an area other than the central portion of thenormal lead frame NLF on which heat is concentrated, the picturerecognition rate of the PRS is improved. Specifically, since heat is notconcentrated on the dent part 16A (FIG. 4D), the plated layer 16B (FIG.4B), or on the support bar 14 (FIG. 4C), the dent part 16A, the platedlayer 16B, and the support bar 14 do not change color thus improving thepicture recognition rate compared to the prior art

[0094]FIG. 2 is a flow chart of the pattern recognition method accordingto another embodiment of the present invention.

[0095] 1. Referring now to FIGS. 2, 5A, 5B and SC, in a lead frameorientation detecting step 200, the number of index holes 1 of thenormal lead frame NLF seated on the heater block is sensed by a sensor,and it is determined whether the normal lead frame NLF is seated in anexact direction. Since the lead frame orientation detecting step 200 isidentical with the lead frame orientation detecting step 1202 (FIG. 12)of the conventional method, its description will be omitted.

[0096] 2. In a first lead frame indexing step 220, the lead eye box andthe lead eye point are set on one tie bar 5 of the normal lead frame NLFby the camera before the normal lead frame NLF is completely clamped onthe heater block with the clamp 400A, and it is determined whether ornot the normal lead frame NLF is seated in an exact position. As thefirst lead frame indexing step 220 is identical with the first leadframe indexing step 1204 (FIG. 12) of the conventional method, itsdescription will be omitted.

[0097] 3. In a second lead frame indexing step 230, the lead eye boxesand the lead eye points are set on two tie bars 5 of the normal leadframe NLF by the camera after the normal lead frame NLF is completelyclamped on the heater block with the clamp 400A, and it is redeterminedwhether or not the normal lead frame NLF is seated in an exact position.As the second lead frame indexing step 230 is identical with the secondlead frame indexing step 1206 (FIG. 12) of the conventional method, itsdescription will be omitted.

[0098] 4. In a VLL step 240, the position of each inner lead 6 of thenormal lead frame NLF is newly captured by the camera and stored in thememory. As the VLL step 240 is identical with the VLL step 1208 (FIG.12) of the conventional method, its description will be omitted.

[0099] 5. In a die orientation detecting step 250, die eye boxes DEBA,DEBB and die eye points DEPA, DEPB are set on specific patterns 32adjacent the edges of the die 30 by the camera, and it is determinedwhether or not the die 30 is mounted in an exact position and directionas discussed further below.

[0100] Initially, a die eye box DEBA, e.g., a first die eye box, and adie eye point DEPA, e.g., a first die eye point, are set on one edge ofthe die 30 by the camera as best shown in FIG. 5B.

[0101] The area of the die eye box DEBA, i.e., the area set as the dieeye box DEBA in the vicinity of the edge of the die 30, is within therange of 1×1 mil˜6×6 mil. In contrast, in the prior art, the die eye boxDEB1 (FIG. 13D) was set to have a wide area of 30×30 mil˜40×40 mil andthe picture inside the die eye box DEB1 was captured and collected asdata. However, the die eye box DEBA of the present invention is set{fraction (1/30)}˜{fraction (6/40)} times smaller than the conventionaldie eye box DEB1 and the picture inside the die eye box DEBA is capturedand collected as data.

[0102] The captured picture is converted and compared with a thirdcontrol picture stored in the memory and a determination is made as towhether the captured picture is identical with the third control picturestored in the memory. If the captured and third control pictures arecompletely identical with each other, the next step is progressed. Ifthe captured and third control pictures are identical with each otherwithin the permitted range, the camera is moved in axes of X and Y tomake the captured and third control pictures be completely identicalwith each other. If there is a difference between the captured pictureand third control picture beyond the permitted range, the operation isstopped and the operator's input is waited for.

[0103] In the above case, the operator sets the die eye box DEBA and thedie eye point DEPA on the die 30 manually.

[0104] Continuously, a die eye box DEBB, e.g., a second die eye box, anda die eye point DEPB, e.g., a second die eye point, are set in thevicinity of another edge of the die 30 by the camera as best shown inFIG. 5C in a similar way, and by performing similar operations as thoseset forth above. A picture inside of the die eye box DEBB is captured.After that, it is determined whether or not the captured picture isidentical with a fourth control picture stored in the memory.

[0105] If the captured and fourth control pictures are completelyidentical with each other, the next step is progressed. If the capturedand fourth control pictures are identical with each other within thepermitted range, the camera is moved in axes of X and Y to make thecaptured and fourth control pictures be completely identical with eachother. If there is a difference between the captured picture and thefourth control picture beyond the permitted range, the operation isstopped and the operator's input is waited for.

[0106] Also, in the above case, the operator sets the die eye box DEBBand the die eye point DEPB on the die 30 manually.

[0107] At this time, the die eye boxes DEBA, DEBB, collectively referredto as die eye boxes DEBs, and the die eye points DEPA, DEPB,collectively referred to as die eye points DEPs, are set on the specificpatterns 32 formed in the vicinity of the edges located outside of thebond pads P of the die 30, in stark contrast to the conventional method.That is, generally, in the vicinity of the edges of the die 30, thespecific patterns 32 such as pictures, figures, characters or numbershaving intrinsic color are formed. In other words, the specific patterns32 formed in the vicinity of the edges of the die 30 have differentshapes from each other. Therefore, if the die 30 having the symmetricalbond pads P is bonded to the die pad 4 in the state of being misalignand rotated at angles of 90 degrees, 180 degrees or 270 degrees, thecaptured pictures and the control pictures stored in the memory aredifferent from each other, and thereby it is directly sensed that thedie 30 is mounted in error.

[0108] Moreover, the die eye boxes DEBs and die eye points DEPs are setoutside the rows, on which the bond pads P are arranged. Therefore, instark contrast to the conventional method, in the present invention, thepicture recognition rate of the PRS is prevented from being reduced bythe probe marks 31 formed on the bond pads P. Namely, even though thebond pads P are pitched finely and the area of the probe marks 31 formedon the bond pads P becomes similar to the area of the bond pads P, sincethe die eye boxes DEBs and die eye points DEPs adopt not the bond pads Pbut the specific patterns 32 formed outside the bond pads P as the basicpicture, the picture recognition rate of the PRS is improved.

[0109] In one embodiment, the die eye boxes DEBs and the die eye pointsDEPs are not overlapped With the passivation layer 33 formed inside therows, on which the bond pads P are arranged. Therefore, in starkcontrast to the conventional method, in the present invention, there isnot caused the reduction of the picture recognition rate of the PRS bythe change of the color of the passivation layer 33.

[0110] Referring now to FIG. 6, continuously, a virtual line 635 isdrawn between the die eye points DEPs and a central point 636 of thevirtual line 635 is compared with a control central point stored in thememory. If the central point 636 is identical with the control centralpoint within the permitted range, the next step is progressed. If not,further steps are stopped and the operator's input is waited for. Atthis time, the operator moves the camera in the axes of X and Y to findthe central point 636 manually.

[0111] Continuously, the position and coordinates of a first bond pad Piis calculated on the basis of the central point 636. That is, as shownin FIG. 6, the position of the first bond pad Pi is calculated from thedie eye points DEPs, and then, the positions of the remaining bond padsP2, . . . , Pn are all calculated.

[0112] In more detail, since the relative or absolute positions of thebond pads P are stored in the memory, if only the coordinate of thefirst bond pad Pi is found exactly, the coordinates of the remainingbond pads P2, . . . , Pn can be automatically found. Through the abovemethod, the coordinates of all bond pads P to be bonded are calculated.

[0113]FIG. 7A shows an example of a die 30A that has been inadvertentlyrotated, e.g., by 90° counterclockwise, and bonded to the normal leadframe NLF, i.e., a misalign die 30A. That is, the picture set on the dieeye box DEBA and the die eye point DEPA of FIG. 5B and the picture seton a first die eye box DEBA1 and a first die eye point DEPA1 of FIG. 7Bare different from each other. Furthermore, the picture set on the dieeye box DEBA and the die point DEPB of FIG. 5C and the picture set on asecond die eye box DEBB1 and a second die eye point DEPB1 of FIG. 7C aredifferent from each other. Therefore, it is detected that thesymmetrical die 30A is incorrectly bonded on the normal lead frame NLFat prescribed angles, i.e., 90 degrees, 180 degrees or 270 degrees, andat this time, the operation is stopped promptly. 6. Referring again toFIGS. 2, 5A, 5B and 5C, in a wire bonding step 260, the general wirebonding is performed in the state that the position and direction of thenormal lead frame NLF and the position and direction of the die 30 areset in prescribed positions.

[0114] Advantageously, since not the bond pads P but the specificpatterns 32 formed adjacent the edges of the die 30 are adopted as thebasic picture, if the symmetrical die 30 is misalign and bonded inrotation at prescribed angles of 90 degrees, 180 degrees or 270 degrees,this misalignment is detected promptly.

[0115] Moreover, even though the bond pads P are pitched finely, sincethe die eye boxes DEBs and the die eye points DEPs adopt not the bondpads P but the specific patterns 32 as the basic picture, the picturerecognition rate of the PRS is improved. Additionally, since the die eyeboxes DEBs and the die eye points DEPs are set on the outercircumference of the bond pads P, on which the passivation layer 33 isnot formed, inaccurate picture information due to the change of thecolor of the passivation layer 33 is not provided, thereby furtherimproving the picture recognition rate by the PRS.

[0116]FIG. 3 is a flow chart of a pattern recognition method accordingto yet another embodiment of the present invention.

[0117] 1. Referring now to FIG. 3, 4A, 4B, 4C, and 4D, in a lead frameorientation detecting step 300, the lead eye box LEBA and the lead eyepoint LEPA are set on the gate 16 of the normal lead frame NLF shownthrough the observation hole 41A of the clamp 400. Further, the lead eyebox LEBB and the lead eye point LEPB are set on the support bar 14 ofthe normal lead frame NLF located on the outer circumference of theclamp 400. This is accomplished by using a camera before the normal leadframe NLF seated on a heater block is clamped completely by the clamp400. A determination is made as to whether or not the normal lead frameNLF is seated in an exact direction and position.

[0118] That is, first, the lead eye box LEBA and the lead eye point LEPAare set on a dent part 16A (FIG. 4D) or a plated layer 16B (FIG. 4B)formed on the gate 16 of the normal lead frame NLF and the pictureinside the lead eye box LEBA is captured. A determination is made as towhether or not the captured picture is identical with the first controlpicture stored in a memory within a permitted range. If the captured andfirst control pictures are completely identical with each other, thenext step is progressed. If the captured and first control pictures areidentical with each other within the permitted range, the normal leadframe NLF is moved in the axes of X and Y to make the captured pictureand the first control picture be completely identical with each other.Meanwhile, if there is difference between the captured picture and thefirst control picture beyond the permitted range, the operation isstopped and an operator's input is waited for. In the above case, theoperator finds the gate 16 of the normal lead frame NLF and sets thelead eye box LEBA and the lead eye point LEPA manually.

[0119] Here, the plated layer 16B is made of at least one of aluminum(Al), silver (Au), gold (Ag), palladium (Pd), nickel (Ni), lead (Pb) andtin (Sn) alloys although other materials are used in other embodiments.

[0120] Continuously, second, the lead eye box LEBB and the lead eyepoint LEPB (FIG. 4C) are set on the support bar 14 of the normal leadframe NLF and the picture inside the lead eye box LEBB is captured. Adetermination is made as to whether or not the captured picture isidentical with the second control picture stored in the memory within apermitted range. If the captured and second control pictures areidentical with each other completely, the next step is progressed. Ifthe captured and second control pictures are identical with each otherwithin the permitted range, the normal lead frame NLF is moved in theaxes of X and Y to make the captured picture and the second controlpicture be completely identical with each other. If there is differencebetween the captured picture and the second control picture beyond thepermitted range, the operation is stopped and the operator's input iswaited for. In the above case, the operator finds the support bar 14 ofthe normal lead frame NLF and sets the lead eye box LEBB and the leadeye point LEPB manually.

[0121] 2. In a lead frame indexing step 320, the lead eye boxes LEBA,LEBB and the lead eye points LEPA, LEPB are set again on the gate 16 andon the support bar 14, respectively, of the normal lead frame NLF by thecamera after the normal lead frame NLF is completely clamped on theheater block with the clamp 400. It is determined again whether or notthe normal lead frame NLF is seated in the exact position to detectwhether or not the position of the normal lead frame NLF changed duringthe clamping of the normal lead frame NLF with the clamp 400.

[0122] That is, first, the lead eye box LEBA and the lead eye point LEPAare set on the dent part 16A or the plated layer 16B formed on the gate16 of the normal lead frame NLF as best shown in FIGS. 4D, 4B,respectively, and the picture inside the lead eye box LEBA is captured.A determination is made as to whether or not the captured picture isidentical with the first control picture stored in the memory within thepermitted range. If the captured and first control pictures arecompletely identical with each other, the next step is progressed. Ifthe captured and first control pictures are identical with each otherwithin the permitted range, the camera is moved in the axes of X and Yto make the captured picture and the first control picture be completelyidentical with each other. Meanwhile, if there is difference between thecaptured picture and the first control picture beyond the permittedrange, the operation is stopped and an operator's input is waited for.In the above case, the operator finds the gate 16 of the normal leadframe NLF and sets the lead eye box LEBA and the lead eye point LEPAmanually.

[0123] Continuously, second, the lead eye box LEBB and the lead eyepoint LEPB (FIG. 4C) are set on the support bar 14 of the normal leadframe NLF and the picture inside the lead eye box LEBB is captured. Adetermination is made as to whether or not the captured picture isidentical with the second control picture stored in the memory withinthe permitted range. If the captured and second control pictures arecompletely identical with each other, the next step is progressed. Ifthe captured and second control pictures are identical with each otherwithin the permitted range, the camera is moved in the axes of X and Yto make the captured picture and the second control picture becompletely identical with each other. If there is difference between thecaptured picture and the second control picture beyond the permittedrange, the operation is stopped and the operator's input is waited for.In the above case, the operator finds the support bar 14 of the normallead frame NLF and sets the lead eye box LEBB and the lead eye pointLEPB manually.

[0124] 3. Referring now to FIGS. 3, 5A, 5B and 5C, in a VLL (Video LeadLocator) step 330, the positions of the inner leads 6 of the normal leadframe NLF are captured by the camera newly and stored in the memory.

[0125] 4. In a die orientation detecting step 340, the die eye boxesDEBA, DEBB and the die eye points DEPA, DEPB are set on the specificpatterns 32 adjacent the edges of the die 30 by the camera, and it isdetermined whether or not the die 30 is mounted in an exact directionand position as discussed further below.

[0126] Initially, the die eye box DEBA and the die eye point DEPA areset on one edge of the die 30 by the camera as best shown in FIG. 5B.

[0127] The area of the first die eye box DEBA, i.e., the area set as thedie eye box DEBA in the vicinity of the edge of the die 30, is withinthe range of 1×1 mil˜6×6 mil. In stark contrast, in the prior art, thedie eye box DEB1 was set to have a wide area of 30×30 mil˜40×40 mil andthe picture inside the die eye box DEB1 was captured and collected asdata. However, the die eye box DEBA of the present invention is set{fraction (1/30)}˜{fraction (6/40)} times smaller than the conventionaldie eye box DEB1 and the picture inside of the die eye box DEBA iscaptured and collected as data.

[0128] The captured picture is converted and is compared with the thirdcontrol picture stored in the memory and a determination is made as towhether the captured picture is identical with the third control picturestored in the memory. If the captured and third control pictures arecompletely identical with each other, the next step is progressed. Ifthe captured and third control pictures are identical with each otherwithin the permitted range, the camera is moved in axes of X and Y tomake the captured and third control pictures be completely identicalwith each other. If there is a difference between the captured pictureand the third control picture beyond the permitted range, the operationis stopped and the operator's input is waited for.

[0129] In the above case, the operator sets the die eye box DEBA and thedie eye point DEPA of the die 30 manually.

[0130] Continuously, the die eye box DEBB and the die eye point DEPB areset in the vicinity of another edge of the die 30 by the camera as bestshown in FIG. 5C in a similar way, and by performing similar operationsas those set forth above. A picture inside of the die eye box DEBB iscaptured. After that, it is determined whether or not the capturedpicture is identical with the fourth control picture stored in thememory.

[0131] If the captured and fourth control pictures are completelyidentical with each other, the next step is progressed. If the capturedand fourth control pictures are identical with each other within thepermitted range, the camera is moved in axes of X and Y to make thecaptured and fourth control pictures be completely identical with eachother. If there is a difference between the captured picture and thefourth control picture beyond the permitted range, the operation isstopped and the operator's input is waited for.

[0132] Also in the above case, the operator sets the die eye box DEBBand the die eye point DEPB of the die 30 manually.

[0133] At this time, the die eye boxes DEBs and the die eye points DEPsare set on the specific patterns 32 formed in the vicinity of the edgeslocated outside of the bond pads P of the die 30, in stark contrast tothe conventional method. That is, generally, in the vicinity of theedges of the die 30, the specific patterns 32 such as pictures, figures,characters or numbers having intrinsic color are formed. In other words,the specific patterns 32 formed in the vicinity of the edges of the die30 have different shapes from each other. Therefore, if the die 30having the symmetrical bond pads P is bonded to the die pad 4 in thestate of being misaligned and rotated at angles of 90 degrees, 180degrees or 270 degrees, the captured pictures and the control picturesstored in the memory are different from each other, and thereby it isdirectly sensed that the die 30 is mounted in error.

[0134] Moreover, it is preferable that the die eye boxes DEBs and thedie eye points DEPs are set outside the rows, on which the bond pads Pare arranged. Therefore, in stark contrast to the conventional method,in the present invention, the picture recognition rate of the PRS isprevented from being reduced by the probe marks 31 formed on the bondpads P. Namely, even though the bond pads P are pitched finely and thearea of the probe marks 31 formed on the bond pads P becomes similar tothe area of the bond pads P, since the die eye boxes DEBs and the dieeye points DEPs adopt not the bond pads P but the specific patterns 32formed outside the bond pads P as the basic picture, the picturerecognition rate of the PRS is improved.

[0135] In one embodiment, the die eye boxes DEBs and the die eye pointsDEPs are not overlapped with the passivation layer 33 formed inside therows, on which the bond pads P are arranged. Therefore, in starkcontrast to the conventional method, in the present invention, there isnot caused the reduction of the picture recognition rate of the PRS bythe change of the color of the passivation layer 33.

[0136] Referring now to FIG. 6, continuously, a virtual line 635 isdrawn between the die eye points DEPs and the central point 636 of thevirtual line 635 is compared with a control central point stored in thememory. If the central point 636 is identical with the control centralpoint within the permitted range, the next step is progressed, but ifnot so, further steps are stopped and the operator's input is waitedfor. At this time, the operator moves the camera in the axes of X and Yto find the central point 636 manually.

[0137] Continuously, the position and coordinate of the first bond padPi is calculated on the basis of the central point 636. That is, asshown in FIG. 6, the position of the first bond pad P1 is calculatedfrom the die eye points DEPs, and then, the positions of the remainingbond pads P2, . . . , Pn are all calculated.

[0138] In more detail, since the relative or absolute positions of thebond pads P are stored in the memory, if only the coordinates of thefirst bond pad Pi is found exactly, the coordinates of the remainingbond pads P2, . . . , Pn can be automatically found. Through the abovemethod, the coordinates of all bond pads P to be bonded are calculated.

[0139] 5. Referring again to FIGS. 3 and 4A, in a wire bonding step 350,the general wire bonding is performed in the state that the position anddirection of the normal lead frame NLF and the position and direction ofthe die 30 are set in prescribed places.

[0140] Advantageously, this embodiment allows detection of when thenormal lead frame NLF is inadvertently rotated at prescribed angles, forexample, 180 degrees, or when the normal lead frame NLF and the invertedlead framed ILF such as that illustrated in FIG. 10B are inadvertentlymixed. Specifically, this is accomplished by setting the lead eye boxesLEBA, LEBB and the lead eye points LEPA, LEPB on specific shaped parts,i.e., on the dent part 16A (FIG. 4D) or the plated layer 16B (FIG. 4B)and the support bar 14 (FIG. 4C), respectively. Thus, the orientation ofthe normal lead frame NLF is detected exactly.

[0141] Furthermore, by setting the lead eye boxes LEBA, LEBB and thelead eye points LEPA, LEPB in areas other than the central portion ofthe normal lead frame NLF on which heat is concentrated, the picturerecognition rate of the PRS is improved.

[0142] Advantageously, since not the bond pads P but the specificpatterns 32 formed on the edges of the die 30 are adopted as the basicpicture, if the symmetrical die 30 is misaligned and bonded in rotationat prescribed angles of 90 degrees, 180 degrees or 270 degrees, thismisalignment is detected promptly.

[0143] Moreover, even though the bond pads P are pitched finely, sincethe die eye boxes DEBs and the die eye points DEPs adopt not the bondpads P but the specific patterns 32 as the basic picture, the picturerecognition rate of the PRS is improved. Additionally, since the die eyeboxes DEBs and the die eye points DEPs are set on the outercircumference of the bond pads P, on which the passivation layer 33 isnot formed, inaccurate picture information due to the change of thecolor of the passivation layer 33 is not provided thereby furtherimproving the picture recognition rate of the PRS.

[0144]FIGS. 8A to 8C are perspective views of clamps 400C, 400D, 400E,respectively, according to various embodiments of the present invention.

[0145] As shown in FIG. 8A, the clamp 400C includes a window 440 formedat the center to expose the die and the ends of the leads adjacent tothe die (not shown) upward and at least one or more observation holes41A and 41B formed at the external circumference of the window 440 toexpose the gate 16 (e.g., the plated layer 16B of FIG. 4B or the dentpart 16A to the FIG. 4D) of the normal lead frame NLF. Although twoobservation holes 41A, 41B are illustrated, in an alternativeembodiment, more or less than two observation holes 41A, 41B are used.Illustratively, two observation holes 41A, 41B are used, one, e.g.,observation hole 41A, is used to expose the gate 16 of the normal leadframe NLF and the other, e.g., observation hole 41B, is used to exposethe gate 16 of the inverted lead frame (ILF) such as that illustrated inFIG. 10B. Therefore, by using the clamp 400C, the orientation, detectionand indexing of the normal lead frame NLF and the inverted lead frameILF can be performed.

[0146] As shown in FIG. 8A, the observation holes 41A and 41B are tworounded through holes. Alternatively, observation holes 41C and 41D areslits as shown in FIG. 8B. As yet a further alternative, an observationhole 41E is an elongated shape as shown in FIG. 8C. The observation hole41E shown in FIG. 8C has a length sufficient to observe each gate 16 ofthe normal lead frame NLF and the inverted lead frame ILF.

[0147] This application is related to Kim et al., co-filed and commonlyassigned U.S. patent application Ser. No. [ATTORNEY DOCKET NUMBERGK0001M] entitled “PATTERN RECOGNITION METHOD”, which is hereinincorporated by reference in its entirety.

[0148] While the present invention has been described with reference tothe particular illustrative embodiments, it is not to be restricted bythe embodiments but only by the appended claims. It is to be appreciatedthat those skilled in the art can change or modify the embodimentswithout departing from the scope and spirit of the present invention.For example, the present invention is described in reference to a normallead frame as the substrate to which the semiconductor dies, sometimescalled chips, are mounted. However, it will be appreciated that othersubstrates such as an inverted lead frame, a printed circuit board, acircuit film, a circuit tape or others on which semiconductor dies aremounted may be applied to the present invention.

[0149] Advantageously, use of the method and clamp in accordance withpresent invention allows detection of when the lead frame isinadvertently rotated at prescribed angles, for example, 180 degrees, orwhen the normal lead frame and the inverted lead framed areinadvertently mixed. Specifically, this is accomplished by setting thelead eye boxes and the lead eye points on specific shaped parts, i.e.,on the dent part or the plated layer of the gate and the support bar.Thus, the orientation of the lead frame is detected exactly.

[0150] Further, by setting the lead eye boxes and the lead eye points inareas other than the central portion of the lead frame on which heat isconcentrated, the picture recognition rate is improved.

[0151] If the die is misaligned and bonded in rotation at prescribedangles, i.e., 90 degrees, 180 degrees or 270 degrees, this misalignmentis detected promptly and further operations are not performed.Therefore, the whole production of the semiconductor packages isimproved and additional steps to bond the misaligned die are notperformed, thereby reducing the manufacturing cost.

[0152] Still further, even though the bond pads are pitched finely,since the die eye boxes and the die eye points adopt not the bond padsbut the specific patterns as the basic picture, the picture recognitionrate of the PRS is improved, and thereby the orientation of the die isdetected exactly.

[0153] Moreover, since the die eye boxes and the die eye points are seton the outer circumference of the bond pads where the passivation layeris not formed, inaccurate picture information due to the change of thecolor of the passivation layer is not provided thereby improving thepicture recognition rate of the PRS. Therefore, the orientation of thedie is detected more exactly.

What is claimed is:
 1. A clamp comprising: a window formed to exposeupward a die mounted on a die pad of a lead frame and leads on an outercircumference of the die on a heater block during a wire bondingprocess; and at least one or more observation holes formed in an outercircumference of the window to set a gate of the lead frame within alead eye box and a lead eye point.
 2. The clamp as claimed in claim 1 ,wherein the at least one or more observation holes are located inopposite positions of the outer circumference of the window to detect anorientation not only of a normal lead frame but also of an inverted leadframe.
 3. A structure comprising: a substrate comprising anunsymmetrical part; and a clamp, the unsymmetrical part being visiblethrough an observation hole of the clamp.
 4. The structure as claimed inclaim 3 wherein the unsymmetrical part comprises a gate.
 5. Thestructure as claimed in claim 3 wherein the unsymmetrical part comprisesa plated layer on a gate.
 6. The structure as claimed in claim 5 whereinthe plated layer comprises a material selected from the group consistingof aluminum, silver, gold, palladium, nickel, lead, and tin alloys. 7.The structure as claimed in claim 3 wherein the unsymmetrical partcomprises a dent part of a gate.
 8. The structure as claimed in claim 3wherein the substrate further comprises a support bar.
 9. The structureas claimed in claim 3 further comprising a camera for setting a lead eyebox and a lead eye point on the unsymmetrical part.
 10. The structure asclaimed in claim 3 wherein the substrate comprises a normal lead frame.11. The structure as claimed in claim 3 wherein the substrate comprisesan inverted lead frame.
 12. The structure as claimed in claim 3 whereinthe substrate is selected from the group consisting of a lead frame, aprinted circuit board, a circuit film, and a circuit tape.
 13. Thestructure as claimed in claim 3 further comprising a die exposed througha window of the clamp.
 14. The structure as claimed in claim 13 whereinleads of the substrate are exposed through the window of the clamp. 15.The structure as claimed in claim 13 wherein the die is a symmetricaldie.
 16. The structure as claimed in claim 13 wherein the die comprisesa specific pattern.
 17. A structure comprising: means for setting afirst lead eye box and a first lead eye point on an unsymmetrical partof a substrate; means for capturing a first picture inside of the firstlead eye box; and means for comparing the first picture to a controlpicture stored in a memory.
 18. The structure as claimed in claim 17wherein the means for comparing comprises means for determining adifference between the first picture and the control picture, thestructure further comprising means for moving the substrate to make thefirst picture be completely identical with the control picture.
 19. Thestructure as claimed in claim 17 wherein the means for setting comprisesa camera and wherein the means for comparing comprises means fordetermining a difference between the first picture and the controlpicture, the structure further comprising means for moving the camera tomake the first picture be completely identical with the control picture.20. The structure as claimed in claim 17 wherein the unsymmetrical partcomprises a gate.
 21. The structure as claimed in claim 17 wherein theunsymmetrical part comprises a dent part of a gate.
 22. The structure asclaimed in claim 17 wherein the unsymmetrical part comprises a platedlayer on a gate.
 23. The structure as claimed in claim 17 wherein thesubstrate comprises a support bar.
 24. The structure as claimed in claim17 further comprising means for clamping the substrate, wherein thefirst lead eye box and the first lead eye point are set on theunsymmetrical part of the substrate through an observation hole of themeans for clamping.
 25. The structure as claimed in claim 17 wherein thesubstrate comprises a lead frame.
 26. A structure comprising: means forsetting a first die eye box and a first die eye point on a specificpattern of a die; means for capturing a first picture inside of thefirst die eye box; and means for comparing the first picture to acontrol picture stored in a memory.